Adjusting means of rotary regenerative sector plate heat exchangers

ABSTRACT

Adjusting means for the sector plate sealing members of rotary regenerative heat exchangers, wherein at least one sensing means is attached to each sealing member, adjacent a circumferential metal flange supported by the regenerator body. The sensing means is connected to a control circuit for actuating a servo device for controlling the position of the sealing member in response to the capacity fluctuations in an electrical circuit comprising the space between the sensing means and the metal flange.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Continuation-In-Part application of U.S. application Ser. No.70,796, filed Aug. 29, 1979, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to an adjusting means for the sector platesealing members of rotary regenerative heat exchangers, and moreparticularly to an adjusting means which, in response to a thermaldeformation of the regenerator body to a dish-like shape of the endsurfaces of the regenerator body and the corresponding variation of thesealing spaces, actuates adjusting linkages of the sealing members bymeans of a servo device so as to maintain a predetermined sealing space,wherein at least one sensing means is attached to each sealing memberadjacent a circumferential or annular metal flange or disc supported bythe regenerator body.

Adjusting means of this type are known for instance from U.S. Pat. No.3,232,335 (Canadian Pat. No. 704,958, GB Pat. No. 1,002,235) in whichthe sensing means are pneumatic, mechanical or magnetic.

One known pneumatic sensing means comprises a nozzle carried by thesealing member, an impingement plate (a circumferential flange) carriedby the regenerator body and means for supplying pressure air to thenozzle, the pressure of the air being dependent on the position of saidnozzle relative to said impingement plate and the servo device beingoperable to adjust the position of the sealing member according to thatpressure.

Another known mechanical sensing means comprises a sensing lever carriedby the sealing member, and a link connecting the lever to a controlmeans for the servo device which is operable to adjust the position ofthe sealing member in response to displacement of the lever which isadapted to slide on a circumferential flange carried by the regeneratorbody.

Still another known magnetic sensing means comprises an electro-magnetlocated to produce a magnetic field between the circumferential flangeand a sealing member, the servo device being operable to adjust theposition of the sealing member according to current variations due tochanges in the strength of the magnetic field, which is dependent on theposition of the sealing member relative to the flange.

In all these known arrangements, the inclusion of a servo device bringsabout the advantage that very large adjustment forces can be produced sothat even in very large size heat exchangers readjustment of the sealingmembers may be effected without difficulties. The smaller forces of themechanical sensing lever are accompanied only by light wear and for thatreason sensing levers of this type have a long working life.

These known arrangements have the disadvantages, however, of beingsubjected to physical and chemical attacks by the impurities containedin the waste flue gases and to the high temperatures of the gasesresulting in a considerable reduction in the life of especially themagnetic sensing means in which the electrical windings or coils andtheir insulating materials are non-resistant to heat.

The object of this invention is to eliminate or at least reduce theabove-mentioned disadvantages.

SUMMARY OF THE INVENTION

The above object has been achieved, according to the invention, in thatthe adjusting means of the kind defined hereinabove is characterized inthat the sensing means is provided with an electrically conductingsensing element which is insulated from the sealing member and which ispositioned close to the metal flange. The sensing element and the metalflange are electrically connected to a control circuit which is arrangedto generate control signals indicating variations of capacity appearingin response to variations of the distance between the metal flange andsaid sensing element, which control signals are supplied to a servodevice for adjusting the position of the sealing members.

In this manner there is provided an adjusting means comprising a sensingmeans that is subject to no wear. Since the sensing means is subjectedto only light corrosion and erosion, its life can be considerablyprolonged by the selection of appropriate heat resistant material.

The sensing means preferably comprises a cylindrical housing having twoends closed by insulating discs. One of the insulating discs, viz. theone facing the regenerator body, supports an electrically conductingsensing disc to which an electric conductor is connected extendingthrough the two insulating discs to a pin plug device at the end of thesensing means facing away from the regenerator body.

A further pin plug device may be located adjacent the first mentionedpin plug device, said further pin plug device being connected to anelectrical temperature sensing device attached to the cylindricalhousing of the sensing means.

The conductor connected to the sensing disc preferably extends with aclearance through the insulating disc closing the end of the cylindricalhousing facing away from the regenerator body, said conductor beinglongitudinally stretched by means of a compression spring and connectedto its pin plug device via a further conductor forming an expansioncurve.

Moreover, according to a preferred embodiment of the invention timedelay means are interconnected in the electrical connection between thehigh frequency amplifier and the servo device controlling the adjustingof the sealing members, which suppress the influences of short-livedfluctuations of capacity, and, hence, prevent the sealing means frombeing subjected to oscillatory motion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a part sectional view of a regenerative heat exchanger havinga rotating regenerator body in which an adjusting means according to theinvention is arranged for the sector plates disposed between theadjacent rotating and non-rotating end surfaces of the regenerative massand the inlet and outlet ducts of each end thereof;

FIG. 2 is a sectional view on a larger scale of a sensing means includedin the adjusting means shown in FIG. 1 for sensing the clearancesbetween the end surfaces of the regenerative mass and the sector platesealing members;

FIG. 3 is a general block diagram of a control circuit of the presentinvention; and

FIG. 4 is a more detailed block diagram of the control circuit of FIG.3.

DETAILED DESCRIPTION

FIG. 1 is a partial sectional view of the right hand part of a rotatingregenerative heat exchanger mounted for rotation about a vertical axis.

A rotating regenerative body 1 is journalled in an upper bearing 3 andin a lower bearing 5 and is enclosed by a housing 7.

The rotatable body 1 is in known manner subdivided into a plurality ofsectorial comparatments and in order to prevent mingling of the twofluid flows there are provided an upper sector plate 9 and a lowersector plate 11 as well as vertical sealing plates 13. The upper andlower sector plates are subdivided into a central section 9a, 11a andouter sections 9b, 11b, the sections being pivotally connected to eachother. The link between the central section 9a and the adjacent outersection 9b of the upper sector plate is adjustable by means of anadjusting rod 15 against the action of a spring member on the upper endwall of the housing. A central portion of the outer section 9b isaccording to the invention provided with a sensing means 17 just above acircumferential metal flange or disc 17' supported by said regeneratorbody 1, and a control circuit 19 which includes a high frequencyamplifier. The signals generated by the control circuit 19 control asolenoid valve 30 connected in a pressure fluid supply conduit 21 of acontrol cylinder 23. Control cylinder 23 controls a control rod 23c viapiston rod 23a and a knee lever 23b under the action of a counterweight,the control rod 23c being connected to the outer end portion of theouter section 9b of the upper sector plate sealing means.

Similar control rod arrangements 25a to 25c with spring means areprovided for supporting and adjusting the vertical sealing plate 13.

The adjusting means of the upper sector plate sealing means, in thiscase positioned in the hot end of the heat exchanger, differs from theadjusting means of the lower sector plate sealing means in the cold endof the heat exchanger. Due to the fact that the rotor containing theregenerative mass when operated undergoes a thermal deformation andadopts a dish-like form, the end surfaces of the rotor will becomeconvex and concave, respectively. Thus, close to the control rodsupporting the link between sections 11a and 11b, there is provided,just underneath a circumferential metal flange or disc 31' attached tothe regenerator body 1, a first sensing means 31 connected to a controlcircuit 33 which includes a high frequency amplifier. The signalgenerated by the control circuit 33 controls a solenoid valve 40 in apressure fluid supply conduit 35 feeding a control cylinder 29 which inthis case actuates the link between lower sector plate section 11a andthe adjacent section 11b in response to the signals generated by thesensing means 31, 31', which link is moved by cylinder 29 over a linkage27 perpendicular to the lower end surface of the regenerator body. Theouter end of the lower sector plate section 11b, just underneath acircumferential flange or disc 37' attached to the regenerator body 1,is also provided with a sensing means 37, connected to a control circuit39 which includes a high frequency amplified. The output signals ofcontrol circuit 39 actuate a solenoid valve 49 in a supply conduit 41 ofa control cylinder 43 controlling via a linkage 45 the position of theouter end of section 11b. Thus, the position of the outer sections 9b ofthe upper section plate sealing means of the hot end of the heatexchanger, which end surface becomes convex, is each controlled by asensing means only; but at the lower sector plates the links betweencontrol sections 11a and the adjacent outer sections 11b as well as theouter ends of the outer sections 11b are each adjusted by a sensingmeans 31, 31'; 37, 37' in response to concave deformation of the lowerend surface of the regenerator body, i.e. the cold end of theregenerator body.

FIG. 2 is a sectional view on a larger scale of a sensing means 17, 17'according to the invention. Sensing means 31, 31' and 37, 37' aresubstantially identical. The sensing means 17, 17' comprises acylindrical housing 50 positioned in a suitable opening of the sectorplate and fixedly attached to said sector plate. Both ends of thehousing 50 are closed by respective insulating discs 52, 54. Disc 52supports an electrically conducting sensing disc 56, suitably made ofmetal, to which an electric conductor 58 is attached, conductor 58extending through control aperturesof the insulating discs 52 and 54.The outer end of conductor 58 (with respect ot the heat exchangerhousing) is provided with a thrust washer 60 which together with acompression spring 64 and a washer 62 applies tension to conductor 58under all thermal conditions. A further conductor section 66 having anexpansion blow connects the outer end of conductor 58 to a pin plugdevice 68 attached to a base plate 70. Base plate 70 is attached tohousing 50 by three supporting arms 72. A temperature sensing device 73is connected via a conductor 74 to a further pin plug device 76 attachedto the base plate 70. The temperature sensing device 73 is designed tocompensate for changes of the dielectric value of the gases independence of the temperature. Sensing disc 17' is coupled to thecorresponding control circuit 19 via a common ground connection. The pinplug device 68, 76 are connected via a cable to the input of acorresponding control circuit which develops control signals which are afunction of the capacitance between sensing discs 56 and 17'. Thecontrol circuit generates amplified control signals which areselectively supplied via conductors to the associated solenoid valves(30, 40, 49) positioned in the pressure fluid supply conduits of thecorresponding control or power cylinders. The valves are actuated andcontrolled by the corresponding control circuit for adjusting theposition of the sealing members during thermal distortion of theregenerator body so as to maintain the sealing members in apredetermined position relative to said regenerator body.

The operating mode of the ajusting device according to the invention isexplained in more detail below.

Each sensing means is coupled to a respective control circuit forgenerating an output control voltage responsive mainly to thecapacitance between two parallel discs (the sensing disc 56 and thecircumferential disc such as 17', 31', 37' attached to the regeneratorbody), and the temperature of the gas present between said two discswhich acts as a dielectric medium.

FIG. 3 illustrates a basic diagram of a control circuit according to thepresent invention. Only control circuit 19 is illustrated, the controlcircuits 33 and 39 being identical thereto. As shown in FIG. 3, thesensing discs 56, 17' are connected to a control circuit 19 whichgenerates a control voltage, such as a stepwise varying DC controlvoltage, as illustrated. The sensing disc 56 is adapted to have itsposition varied in the direction of the arrow A shown in FIG. 3 relativeto the annular disc 17'. Due to the variations in position of disc 56relative to disc 17'. Due to the variations in position of disc 56relative to disc 17', the electrical capacitance therebetween varies andthese variations in electrical capacitance are sensed by the controlcircuit which generates a corresponding control output voltage. In otherwords, the control output voltage of control circuit 19 is dependentupon the distance or spacing between the sensing metallic discs 17' and56 of the sensing means. The annular sensing discs or electrodes 17',31' and 37' are supported by the various portions of the regeneratorbody as shown in FIG. 1. The control circuit can also be thought of aselectro-mechanical converters which generate an electrical controlsignal responsive to a sensed mechanical relative movement.

Referring to FIG. 4, the control circuit comprises a crystal controlledoscillator 80 which generates an A.C. voltage having a constantfrequency. The output of the oscillator 80 is coupled to an amplifier 81which also receives modulation inputs from a resonance circuit 82, theresonance circuit being controlled by the capacitance between sensingdiscs or electrodes 56, 17'. The capacitance between sensing discs 56,17', which is result of the relative displacement therebetween, changesthe resonance frequency of the resonance circuit 82 as a function ofsaid displacement or variation of capacitance. The capacitance is alsodependent on the temperature of the gas between the sensing discs 56,17', and in order to compensate for variations of said temperature thetemperature sensing device 73 is connected via conductor 74 and pin plugdevice 76 to a further input terminal of said resonance circuit 82. Theamplifier 81 generates a modulated A.C. voltage having a constantfrequency and an amplitude which is modulated as a function of thevarying resonance frequency of the resonance circuit 82. The modulatedA.C. voltage is rectified in a rectifier circuit 83 and the rectifiedvoltage is coupled to a low pass filter 84 and then to a discriminator85. The output of the discriminator 85 is the control voltage forcontrolling the associated control cylinder 23, 29, 43 via therespective valves 30, 40 and 49.

The control signals actuate the solenoid-type valves such that thecorresponding control or power cylinders are connected to the pressurefluid supply or to the pressure fluid outlet (not pressurized) in orderto maintain said predetermined clearance between the sealing means 9, 13and regenerator body during all types of thermal deformation of theregenerator body (called rotor "turn-down").

The solenoid-type valves may be termed generally as "servo-operated"valves. They may be replaced by motor operated valves which aregenerally known as servo-type valves.

The cylindrical housing 50 preferably is made of metal and theinsulating discs 52, 54 of alumina (alumina oxide). In order to minimizethe self-capacity of the sensing means the inner diameter of the housing50 preferably is 80 to 120 mm and the diameter of the conductor 58 ispreferably 3 to 5 mm.

Although the invention has been described with reference to heatexchangers having a rotatable regenerator body 1 and stationary ducts,it is evident that it is applicable also to such regenerative heatexchangers having a stationary regenerator body and rotatable ducts.

I claim:
 1. In adjusting means for a rotary regenerative heat exchanger,the head exchanger comprising a regenerator body and ducts, saidregenerator body and ducts being rotatable relative to each other, saidregenerator body having sector plates, sector plate sealing members andat least one circumferential metal flange supported by said regeneratorbody:said adjusting means comprising adjusting linkages coupled to saidsealing members for adjusting said sealing members, linkage actuatingmeans coupled to said adjusting linkages of said sealing members andwhich, in response to a thermal deformation of the regenerator body todish-like shape of the end surfaces of the regenerator body and thecorresponding variation of the sealing spaces, actuates said adjustinglinkages of said sealing members so as to maintain a predeterminedsealing space, and at least one sensing means coupled to each sealingmember, adjacent said circumferential metal flange supported by theregenerator body; the improvement wherein said sensing means comprisesan electrically conducting sensing element (56) which is insulated fromthe respective sealing member and which is positioned close to butspaced from said circumferential metal flange, a control circuit, (19;39; 33) electrically coupled to said sensing element (56) and to saidcircumferential metal flange (17', 31', 37') for generating controlsignals indicating variations of electrical capacity which result inresponse to variations of the distance between said circumferentialmetal flange and said sensing element (56), said control signals beingsupplied to said linkage actuating means for controlling the ajusting ofsaid sealing members (9; 11).
 2. The adjusting means of claim 1, whereineach of said sensing means (17; 31; 37) comprises a cylindrical housing(50) having two opposing ends, two insulating elements (52; 54)respectively closing said two opposing ends of said housing, one of saidinsulating elements (52) facing said regenerator body (1) and supportingsaid sensing element (56), a first pin plug device (68) at the end ofsaid sensing means facing away from said regenerator body, and anelectrical conductor (58) connected to said sensing element (56) andextending through said two insulating elements to said first pin plugdevice (68).
 3. The adjusting means of claims 1 or 2 wherein saidsensing element (56) is a sensing disc.
 4. The adjusting means of claim2 wherein each of said sensing means further comprises a further pinplug device (76) located adjacent said first pin plug device (68), anelectrical temperature sensing device (73) attached to said cylindricalhousing (50) coupled to said further pin plug device (76), said controlcircuit being coupled to said further pin plug device (76).
 5. Adjustingmeans as claimed in claim 2 wherein said conductor (58) connected to thesensing element (56) extends with a clearance through the other of saidinsulating elements (54) which closes the end of said cylindricalhousing facing away from said regenerator body, a compression spring(64) coupled to said conductor (58) for longitudinally stretching saidconductor between said two insulating elements (52, 54), and a furtherconductor (66) forming an expansion curve coupling said conductor (58)to said first pin plug device (68).
 6. The adjusting means of any one ofclaims 1, 2, 4 or 5 wherein said linkage actuating means includes servomeans coupled to said high frequency amplifier for controlling theadjusting of said sealing members.
 7. The adjusting means of claim 6wherein said servo means comprises a solenoid type valve in a pressurefluid supply to a linkage actuating means.